This invention relates generally to circuit breakers and, more particularly, to thermal circuit breakers.
Circuit breakers are electrical circuit protective devices that interrupt a flow of current when the current exceeds a specified value, sometimes referred to as an overcurrent value. In an overcurrent condition, the circuit breaker rapidly separates a pair of contacts that normally conduct the current. Circuit wiring and associated circuit components may therefore be isolated from potentially damaging and undesirable exposure to excess currents. Conventionally, the circuit breakers are either thermally or magnetically actuated.
One type of known thermal circuit breaker includes a nonconductive housing with conductive line and load contact terminals therein for electrical connection to a circuit to be protected. A temperature responsive element, sometimes referred to as thermal trigger element, is extended across the line and load contacts, and when the breaker is connected to an energized circuit, current flows between the breaker contacts through the trigger element in normal operation. Current flow through the trigger element heats the trigger element, and when current flow exceeds a predetermined level, the trigger element trips, deflects, or deforms to an activated position separated from each of the breaker contacts, thereby breaking the current through the breaker and protecting load side electrical devices.
While thermal circuit breakers for interrupting DC current, such as those for auxiliary and accessory circuits for recreational vehicles and marine applications, are commercially available, known circuit breakers tend to be rated for protecting xe2x80x9clow ampxe2x80x9d circuits of about 50 amps or less in 30 Vdc electrical systems or less, or rated for interrupting xe2x80x9chigh ampxe2x80x9d currents substantially greater than 50 amps, such as 100 amps or more in 30 Vdc electrical systems. In mid-range applications between these extremes, e.g., current values up to about 60 amps, low amp breakers are inadequate for use while high amp breakers are over designed and hence not efficient or cost effective. An alternative breaker construction for mid-range applications is therefore desired.
Additionally, some thermal circuit breakers include manual reset and manual trip features to interrupt the breaker circuit independently of thermal conditions. Implementing such features can lead to relatively complicated constructions that increase manufacturing and assembly costs of the breaker.
In one aspect a circuit breaker is provided that comprises a base housing comprising a contact cavity therein, first and second terminals at least partially located within said contact cavity, and a thermal trigger element fixedly coupled to said first terminal and in electrical contact with said second terminal in normal operation. The thermal element is configured to activate and break electrical contact with said second terminal upon a predetermined current condition.
In another aspect, a circuit breaker is provided that comprises a base housing comprising a contact cavity therein, first and second terminals at least partially located within said contact cavity, a thermal trigger element extending between said first and second terminals, and a reset actuator situated within said contact cavity. The reset actuator comprises a shaft and a reset ledge extending from said shaft, said trigger element contacting said reset ledge when trigger element is activated, thereby rotating said shaft.
In yet another aspect, a circuit breaker is provided that comprises a base housing comprising a contact cavity therein, first and second terminals at least partially located within said contact cavity, a thermal trigger element extending between said first and second terminals, and a trip actuator situated within said contact cavity. The trip actuator comprises at least one leg, a stabilizer coupled to said leg, and an engagement surface offset from said stabilizer to produce pivoting movement about the stabilizer.
In another aspect, a circuit breaker is provided. The circuit breaker comprises a base housing comprising a contact cavity therein, first and second terminals at least partially located within said contact cavity, a thermal trigger element fixedly coupled to said first terminal and in electrical contact with said second terminal in normal operation, said thermal element configured to activate and break electrical contact with said second terminal upon a predetermined current condition, and a cover comprising attached to said base, said cover comprising an outer surface and an overmolded gasket substantially covering said outer surface.
In another aspect, a circuit breaker for mounting to an electrical distribution panel is provided. The circuit breaker comprises a base housing comprising a contact cavity therein and a lower outer periphery, first and second terminals at least partially located within said contact cavity, and a thermal trigger element in electrical contact with said first terminal and said second terminal in normal operation, said thermal element configured to activate and break electrical contact with said second terminal upon a predetermined current condition. A cover assembly is attached to said base housing and comprises an upper outer periphery, said upper outer periphery and said lower outer periphery shaped to be received in a single panel cut-out pattern.